Kaikohe,
I'm all for being cautious, particularly where the manufacturer provides no guidance, but in this case I'm happy to proceed where the contamination is as described in the flight manual as being safe to proceed. The reality is that if you fly regularly, you will have almost certainly paxed on an aircraft with some level of acceptable wing contamination due to ice.
Last edited by OneDotLow; 4th Jul 2013 at 11:00.